372 M. M. Mercaur 
separate; they may be connected by such delicate strands as are found uniting 
the daughter cells in late stages of division). Figs. 252—254 acetic-carmine; 
Figs. 255 and 256 from life. > 440 diameters. 
Figs. 257 and 258. Macrogametes (Fig. 257 possibly a macrogamete parent- 
cell) from a tadpole of Bombinator pachypus (?), infected 22 hours. The first 
figure shows the usual size, the second the smallest size found. The ectosare 
spherules are indicated. Acetic-carmine. < 673 diameters. 
Fig. 259. A microgamete from the same tadpole of Bombinator pachypus (?), 
infected 22 hours. LEctosare spherules (unshaded) and endosare spherules (shaded) 
are shown. In no other series of infections have I found apparently mature gametes 
before 42 hours after the beginning of infection. Acetic-carmine. >< 990 diameters. 
Fig. 260. A macrogamete (or macrogamete parent-cell?) from the same tad- 
pole of Bombinator pachypus (?), infected 22 hours. The ectosare spherules are 
shown. Acetic-carmine. > 673 diameters. 
Fig. 261. A living but almost quiescent microgamete. > 673 diameters. 
Infection data were not noted. 
Fig. 262. A free-hand drawing of a living copulating pair from a tadpole 
of Bufo vulgaris, infected 66 hours. 
Plate XXVII 
Opalina caudata and Opalina dimidiata. 
All figures are reduced one-third, to the magnification indicated. 
Figs. 263—276. Opalina caudata. 
Fig. 263. <A copulating pair from a tadpole of Bufo vulgaris infected 66 hours. 
The macrogamete is in division. Free-hand drawing. 
Figs. 264—271. Examples of copulation in living animals from tadpoles of 
Bombinator pachypus, infected 60 hours. Fig. 265 shows a late stage of copulation; 
Figs. 269 and 270 show copulation while the macrogamete is in division; Fig. 271 
shows two males attached to one female. Fig. 264 > 438 diameters; the other 
figures are free-hand drawings. 
Figs. 272—274. Copulating pairs from a tadpole of Bombinator pachypus 
infected 60 hours. The endosare spherules are drawn in Figs. 272 and 273. Each 
nucleus in Figs. 273 and 274 shows three chromosomes. The nature of the body 
just outside the microgamete nucleus in Fig 272 is uncertain. Acetic-carmine. 
< 673 diameters. 
Fig. 275. A pseudocyst (macrogamete?) from a tadpole of Rana esculenta, 
infected with both O. caudata and O. intestinalis by being placed for an hour in 
a jar with adult Bombinator pachypus. Cast off cilia and extruded globules lie 
around the pseudocyst. Each nucleus has three chromosomes. X 6/3 diameters. 
Fig. 276. Abnormal copulation of two individuals of nearly similar size, the 
smaller of which showed a nucleus in division. Acetic-carmine. Infection data 
and the magnification were not noted. 
Figs. 277—298. Opalina dimidiata. 
Figs. 277—281. Minute individuals from a culture in 0,6°/, NaCl solution, 
kept three days after removal of the animals from the rectum of an adult Rana 
esculenta. Division continued during this time and many of the animals became 
minute, as shown, and were apparently ready for encystment. Fig. 277 shows 
